package arm.format.pako.zlib;

import haxe.io.UInt8Array;

// Note: adler32 takes 12% for level 0 and 2% for level 6.
// It doesn't worth to make additional optimizationa as in original.
// Small size is preferable.

class Adler32
{
  static public function adler32(adler:Int, buf:UInt8Array, len:Int, pos:Int):Int {
    var s1 = (adler & 0xffff) |0,
        s2 = ((adler >>> 16) & 0xffff) |0,
        n = 0;

    while (len != 0) {
      // Set limit ~ twice less than 5552, to keep
      // s2 in 31-bits, because we force signed ints.
      // in other case %= will fail.
      n = len > 2000 ? 2000 : len;
      len -= n;

      do {
        s1 = (s1 + buf[pos++]) |0;
        s2 = (s2 + s1) |0;
      } while ((--n) != 0);

      s1 %= 65521;
      s2 %= 65521;
    }

    return (s1 | (s2 << 16)) |0;
  }
}